Ratings erosion on “American Idol” has ignited speculation that Paula Abdul could return next season when Simon Cowell leaves the show.

While “Idol” remains a ratings winner, its slip has begun to show thanks to ABC’s “Dancing With the Stars.”

For the last two weeks (March 29 and April 5), the Monday-night edition of “Dancing” has beaten both editions of “Idol” (Tuesday and Wednesday) in total viewers. (“Idol” has beaten “Dancing” in head-to-head battle on Tuesdays.)

It’s the first time in five years that any show has beaten both installments of “Idol” for two consecutive weeks, and the ratings shift has fanned rumors regarding Abdul — a fan favorite who left “Idol” after last season and was replaced by Ellen DeGeneres.

In Touch magazine quoted an insider saying that “Idol” producers “want Paula back. They’re not sure if she’d be the fifth judge, but they are talking to her. The show is just not as much fun to watch without her.”

Abdul hasn’t yet committed to any new projects, despite reported dalliances with ABC to appear on “Dancing” and to host a dance show.

Industry insiders believe Abdul will likely join her “Idol” pal Cowell when he launches the US version of his British hit, “The X-Factor,” on Fox in September 2011. Cowell has said publicly he’d love to work with Abdul again.

“Paula has not been asked [to come back to ‘Idol’],” Abdul’s publicist, Jeff Ballard, told The Post yesterday.

“She was completely unaware of that rumor and laughed when she heard about it.”

Fox officials declined to comment yesterday.

“Idol” executive producer Cecile Frot-Coutaz, during a conference call with reporters to discuss “Idol Gives Back,” said there’s “no truth” to the rumor.